Lycopodiaceae

“ The Ovule, Endosperm, Corpuscle, and Embryonic vesicle are to the Coniferae and Cycadae what the Large Spore, Prothallus, Archegonium, and Embryo-cell are to the Lycopods, the pollen of the Gymnospermae corresponding to the small spores of the Lycopodiaceae: the reproductive organs of Lycopodiaceae and Gymnospermae are, therefore, essentially the same. The higher plants differ from these orders in that the embryo-sac contains the embryo-cell only ”

“ The central cylinder of the root often shows a striking resemblance to that of the stem. The Lycopodiaceae are homosporous. The spores are formed in sporangia of considerable size, situated on the upper surface and near the base of the sporophylls. The latter may differ from the foliage leaves and be arranged in definite cones, or the two may be similar and occupy alternate zones of a shoot with continued growth ”

“ The Equisetaceae (horsetails) which also first appear in the Silurian and reach their maximum development in the Coal formation, are, in all succeeding formations, far less numerous than ferns, and only thirty living species are known. Lycopodiaceae, though still more abundant in the Coal formation, are very rarely found in any succeeding deposit, though the living species are tolerably numerous, about 500 having been described. ”

“ This tribe at the present day, contains no species more than three feet high, but the greater part of them are weak, or creeping plants, while their earliest fossil representatives appear to have attained the dimensions of Forest Trees. [16]
Existing Lycopodiaceæ follow nearly the same law as ferns and Equisetaceæ, in respect of geographical distribution; being largest and most abundant in hot and humid situations within the Tropics, especially in small islands. ”

“ And with the first indications of land we pass direct from the Thallogens to the Acrogens,—from the sea weeds to the fern allies. The Lycopodiaceæ;, or club mosses, bear in the axils of their leaves minute circular cases, which form the receptacles of their spore-like seeds. And when, high in the Upper Silurian System, and just when preparing to quit it for the Lower Old Red Sandstone, we detect our earliest terrestrial organisms, we find that they are composed exclusively of those little spore receptacles. The number of land plants gradually increases as we ascend into the overlying system. ”

“ On the contrary, the lower members of each tend to converge towards the lower members of all the others. The same may be said of the vegetable world. The apparently clear distinction between flowering and flowerless plants has been broken down by the series of gradations between the two exhibited by the Lycopodiaceæ, Rhizocarpeæ, and Gymnospermeæ. The groups of Fungi, Lichenes, and Algæ have completely run into one another, and, when the lowest forms of each are alone considered, even the animal and vegetable kingdoms cease to have a definite frontier. ”

“ The engraving (Fig. 38) represents one of these gigantic mare’s-tails, or Calamites, of the Coal-period, restored under the directions of M. Eugene Deslongchamps. It is represented with its fronds of leaves, and its organs of fructification. They seem to have grown by means of an underground stem, while new buds issued from the ground at intervals, as represented in the engraving.
The Lycopods of our age are humble plants, scarcely a yard in height, and most commonly creepers; but the Lycopodiaceæ of the ancient world were trees of eighty or ninety feet in height. ”

“ Lycopodiaceæ, lī-ko-pō-di-ā′se-ē, n.pl. a class of isoporous vascular cryptogams, having mostly a dichotomous form of branching—its typical genus Lycopō′dium.—n. Ly′copode, a highly inflammable yellow powder made up of the spores of Lycopodium. [Gr. lykos, a wolf, pous, the foot.]
Lyddite, lid′īt, n. a powerful explosive made (at Lydd in Kent) from picrate of potash.
Lydian, lid′i-an, adj. pertaining to Lydia in Asia Minor: of an ancient Greek mode of music: (mus.) soft and slow: luxurious and effeminate. ”

“ Even if we make some reduction on the ground of varieties which have been mistaken, in the absence of their fructification, for species, still the result is singular, because the whole of Europe affords at present no more than sixty-seven indigenous species.
Lycopodiaceæ—Lepidodendron.—About forty species of fossil plants of the Coal have been referred to this genus, more than half of which are found in the British coal-measures. They consist of cylindrical stems or trunks, covered with leaf-scars. In their mode of branching, they are always dichotomous (see Fig. 454) . ”

“ Stems prostrate or slightly arching:, 6'-16' long, simple or rarely branched, leafy; peduncles 4'-12' long, slender, rigidly erect, arising directly from the creeping stem, terminated by a slender spike 9"-23⁄4' long; leaves of the stem lanceolate-acuminate, curved upwards, irregularly toothed, sometimes doubly so; leaves of the peduncle more slender, incurved, mostly appressed, yellowish green or stramineous, the lower ones sharply toothed, the upper ones entire or nearly so; sporophyls mostly incurved and subappressed, abruptly subulate from an ovate more or less toothed base. ”

“ Lycopodium. It would be out of place in a volume devoted mainly to fossil plants to attempt a comprehensive account of the general morphology of recent species, and indeed our knowledge of the anatomical characters of the genus is still somewhat meagre. For purposes of comparison with extinct types, it is essential that some of the more important morphological features of existing species should be briefly considered. The additions made to our knowledge of the gameophyte [92] of European and tropical species during the last two decades have revealed a striking diversity in habit. ”

“ Stems rising 2’-4’ from a curved or decumbent base, 1-3 times dichotomous, the branches forming a rather close tuft of densely leafy vertical stems; leaves spreading or somewhat deflexed, entire or minutely denticulate, arranged in alternating series of longer and shorter, the former linear to linear-lanceolate, slightly broader above the middle, alternate, the latter distinctly broadest at the base, gradually tapering to an acuminate apex, and more often bearing the sporanges; plant often gemmiparous. ”

“ Lepidodendra, twigs of Bothrodendron [169] species of conifers, fern rhizomes, and Aphlebiae [170] have masqueraded as herbaceous lycopods. It is obvious that an attempt to identify fossils presenting a general agreement in habit and leaf-form with recent species of lycopods must be attended with considerable risk of error. Recent Conifers include several species the smaller branches of which simulate the leafy shoots of certain species of Lycopodium and Selaginella, and it is not surprising to find that this similarity has been responsible for many false determinations. ”

“ Lycopodium, represented by nearly 100 species, forms a constituent of most floras: epiphytic species predominate in tropical regions, while others flourish on the mountains and moorlands of Britain and in other extra-tropical countries. For the most part Lycopodium exhibits a preference for a moist climate and appears to be well adapted to habitats where the amount of sunlight is relatively small and the conditions of life unfavourable for dense vegetation. Mountains and islands constantly recur as situations from which species have been recorded. ”

“ A number of species of Lycopodium are epiphytic and those of Isoëtes live submerged in water. Vegetative reproduction is effected in various ways: by the separation of the branches of a creeping stem in some Lycopodia, the persistence through the winter of the apex of the shoot in L. inundatum, and by the formation of leafy bulbils on the aerial stem of L. Selago and others. A highly specialized means of vegetative reproduction is seen in the tubers of Phylloglossum and the embryos of some Lycopods. The modifications shown by the gametophyte of Lycopodium will be described below. ”

“ The simple leaves, which are of small size and do not possess a ligule, are arranged spirally around the branched stem in the majority of the species. The roots of the erect forms often grow downwards in the cortex of the stem to reach the soil. The anatomy of Lycopodium presents considerable variety in detail, but the stem is always monostelic and the development of the xylem centripetal, the protoxylems being situated at the periphery of the stele; pericycle and endodermis surround the stele, and the wide cortex may be more or less sclerenchymatous. ”

“ A description by Mr Rodway [237] of Lycopods on the border of a savannah in Guiana forming a miniature forest of Pine-like Lycopodiums might, with the omission of the qualifying adjective, be applied with equal force to a grove of Lepidodendra. The equal dichotomy of many of the branches gave to the tree a habit in striking contrast to that of our modern forest trees, but, on the other hand, in close agreement with that of such recent species of Lycopodium as L. cernuum (fig. 123) , L. obscurum (fig. 124) and other types. ”

“ Isoetes (fig. 132) , of which Mr Baker in his Handbook of the Fern-Allies enumerates 49 species, is a type apart, differing in habit as in certain other characters from the other members of the Lycopodiales. Some botanists [89] prefer to include the genus among the Filicales, but the balance of evidence, including resemblances between Isoetes and extinct Lycopodiaceous plants, would seem to favour its retention as an aberrant genus of the group Lycopodiales. Some species are permanently submerged, others occur in situations intermittently covered with water, and a few grow in damp soil. ”

“ The vegetable remains are very numerous, and in a state of beautiful preservation. Nowhere, indeed, in the best arranged herbarium, have we anything so graceful, so minutely and skillfully delineated, as are the figures of these plants upon the stone. There are several species of lycopodium; also stigmaria, sigillaria, equisetum, calamus, and cyclopteris, in great abundance. The fronds of the fossil sphenopteris furnish exquisite tracings of nature’s penciling. Nor are the relics belonging to the animal kingdom less remarkable for their freshness and variety. ”

“ The sexual organs are represented by antheridia and archegonia; 32the male cells are provided with two cilia except in Isoetes which has multiciliate antherozoids like those of the ferns.
The existing Lycopods, though widely distributed, never grow in sufficiently dense masses to the exclusion of other plants to form a conspicuous feature in the vegetation of a country. The inconspicuous rôle which they play among the plant-associations of the present era affords a striking contrast to the abundance of the arborescent species in the Palaeozoic forests of the northern hemisphere. ”

“ The danger which should be borne in mind, in adopting as a matter of convenience the term herbaceous as a sectional heading, is that it should not be taken to imply a complete inability of the so-called herbaceous types to make secondary additions to their conducting tissues. The specimens on which the species of Lycopodites and Selaginellites, (genera which may be designated herbaceous,) are founded are preserved as impressions and not as petrifications; we can, therefore, base definitions only on habit and on such features as are shown by fertile leaves and sporangia. ”

“ In its lowest fossiliferous beds we detect a Lycopodite which not a little resembles one of the commonest of our club mosses,—Lycopodium clavatum,—with a minute fern and a large striated plant resembling a calamite, and evidently allied to an existing genus of Acrogens, the equisetaceæ. In the Middle Old Red Sandstone there also occurs a small fern, with [Pg 42] some trace of a larger; and one of its best preserved vegetable organisms is a lepidodendron,—an extinct ally of the Lycopodiums ”

“ This centripetal or root-like character of the primary xylem is an important feature in recent as in fossil Lycopods. The close agreement between the roots and stems of recent species in the disposition of the vascular elements also denotes a simpler type of anatomy 41than occurs in the majority of vascular plants in which stem and root have more pronounced structural peculiarities. A pericycle, 2–6 cells in breadth, encloses the xylem and phloem bands and this is succeeded by an endodermis, 2–3 cells broad, with vaguely defined limits. ”

“ From a botanical point of view the various records of Lycopodites and Selaginellites have but a minor importance; they are not sufficiently numerous to throw any light on questions of distribution in former periods, nor is the preservation of the material such as to enable us to compare the fossil with recent types either as regards their anatomy or, except in a few cases, their sporangia and spores. The Palaeozoic species are interesting as revealing less reduction in the number of spores produced in the megasporangia. ”

“ In several species, grouped round the widely distributed type Lycopodium Selago Linn., the comparatively short, erect or suberect, shoots form fairly compact tufts; the ordinary foliage-leaves function as sporophylls, and the sporangia are not localised on special portions of shoots. From this type, we pass to others in which the fertile leaves tend to be confined to the tips of branches, but hardly differ in form from the sterile. ”

“ As far as number is concerned, the living Club Mosses represent a comparatively insignificant group when compared with the Ferns. In all the world there are probably not more than five or six hundred species. These are very widely distributed, and there is hardly any part which cannot offer at least a few species. We have five species of Lycopodium in the United Kingdom. All are rather local, though often enough they occur in great abundance in special localities. ”